Low power, high resolution solid state LIDAR circuit having a modulator to modulate a bit sequence onto a carrier frequency of a received optical signal

ABSTRACT

An optical circuit includes solid state photonics. The optical circuit includes a phased array of solid state waveguides that perform beamsteering on an optical signal. The optical circuit includes a modulator to modulate a bit sequence onto the carrier frequency of the optical signal, and the beamsteered signal includes the modulated bit sequence. The optical circuit includes a photodetector to detect a reflection of the beamsteered optical signal. The optical circuit autocorrelates the reflection signal with the bit sequence to generate a processed signal.

PRIORITY

This application is a continuation of, and claims the benefit ofpriority of, U.S. patent application Ser. No. 14/998,183, filed Dec. 26,2015.

FIELD

Embodiments of the invention are generally related to optical devices,and more particularly to LIDAR (light detection and ranging) devices.

COPYRIGHT NOTICE/PERMISSION

Portions of the disclosure of this patent document may contain materialthat is subject to copyright protection. The copyright owner has noobjection to the reproduction by anyone of the patent document or thepatent disclosure as it appears in the Patent and Trademark Officepatent file or records, but otherwise reserves all copyright rightswhatsoever. The copyright notice applies to all data as described below,and in the accompanying drawings hereto, as well as to any softwaredescribed below: Copyright © 2015, Intel Corporation, All RightsReserved.

BACKGROUND

There is an increasing demand for three dimensional (3D) video or imagecapture, as well as increasing demand for object tracking or objectscanning. Thus, the interest in 3D imaging is not simply to sensedirection, but also depth. Longer wavelength signals (such as radar)have wavelengths that are too long to provide the sub-millimeterresolution required for smaller objects and for recognition of fingergestures and facial expressions. LIDAR (light detection and ranging)systems use optical wavelengths, and can provide finer resolution. Abasic LIDAR system includes one or more light sources andphotodetectors, a means of either projecting or scanning the lightbeam(s) over the scene of interest, and one or more control systems toprocess and interpret the data. Scanning or steering the light beamtraditionally relies on precision mechanical parts, which are expensiveto manufacture, and are bulky and consume a lot of power.

A known issue with ranging systems based on reflected signals is thatdetection relies on collecting reflected signal energy from diffusesurfaces. It is known that scattered optical power degrades as thesquare of the distance, and since the probe light scatters in alldirections off the target object this leads to limitations on the rangeover which a reflected signal can be detected with sufficientsignal-to-noise ratio (SNR). The range can be improved by increasing thesize of the receiver collection optics, which allows for capturing moreof the reflected signal, but the increased size limits application ofthe device. Collection of optical pulses over a long period of timetogether with techniques such as averaging or narrowband filtering canalso be used to increase SNR, but such techniques require increaseddwell time on a portion of the field of view, thus limiting the framerate with which the system can monitor the target. Additionally, theperiodic nature of the pulse patterns leads to ambiguity in the timingof the returned signal, which increases ambiguity with respect to theprecise range to the target.

Finally, recording the range to the target with high precision isdependent on the precision with which the timing of returned pulses canbe recorded. The timing with which the returned pulses can be recordedin turn either requires pulse widths comparable to the depth resolution,or requires that the pulses be recovered with sufficient SNR todistinguish their peak from the rest of the pulse. This tradeoff betweenpulse width, dwell time, and SNR is known as the Cramer-Rao lower bound.Thus, obtaining a usable echo in implementation requires a certainminimum energy to be transmitted in order to maintain sufficient signalto noise ratio for detection of the target.

To capture sufficient reflected power to detect objects at severalmeters distance at even VGA (video graphics array) resolution and framerates using compact collection optics traditionally requires the use oftransmit powers that pose eye-safety risks. In addition to posing risksfor eye safety, such high-power transmit or output power is incompatiblewith portable or wearable devices. However such systems are typicallynot easily integrated into a small form-factor together with a means ofscanning the optical beam across the field of view.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description includes discussion of figures havingillustrations given by way of example of implementations of embodimentsof the invention. The drawings should be understood by way of example,and not by way of limitation. As used herein, references to one or more“embodiments” are to be understood as describing a particular feature,structure, and/or characteristic included in at least one implementationof the invention. Thus, phrases such as “in one embodiment” or “in analternate embodiment” appearing herein describe various embodiments andimplementations of the invention, and do not necessarily all refer tothe same embodiment. However, they are also not necessarily mutuallyexclusive.

FIG. 1 is a block diagram of an embodiment of a system with anintegrated solid state LIDAR circuit.

FIG. 2 is a block diagram of an embodiment of a system with anintegrated solid state LIDAR circuit that autocorrelates a reflectionsignal with a known bit sequence.

FIG. 3A is a block diagram of an embodiment of a photonic system thatautocorrelates a reflection signal with a known bit sequence, with asingle transmitter and receiver I/C.

FIG. 3B is a block diagram of an embodiment of a photonic system thatautocorrelates a reflection signal with a known bit sequence, withseparate transmitter and receiver I/Cs.

FIG. 4 is a block diagram of an embodiment of a top view of anintegrated solid state LIDAR circuit.

FIGS. 5A-5B are block diagrams of an embodiment of cross sections of anintegrated solid state LIDAR circuit.

FIG. 6 is a diagrammatic representation of a pseudorandom bit sequencemodulated onto a phased LIDAR output signal for an embodiment of aphotonic integrated circuit.

FIG. 7 is a diagrammatic representation of a plot of signal to noise forpseudorandom bit sequences of different bandwidth for an embodiment of asolid state LIDAR circuit.

FIG. 8 is a flow diagram of an embodiment of a process for imaging witha solid state LIDAR circuit.

FIG. 9 is a block diagram of an embodiment of a computing system inwhich a low power, high resolution solid state LIDAR circuit can beimplemented.

FIG. 10 is a block diagram of an embodiment of a mobile device in whicha low power, high resolution solid state LIDAR circuit can beimplemented.

Descriptions of certain details and implementations follow, including adescription of the figures, which may depict some or all of theembodiments described below, as well as discussing other potentialembodiments or implementations of the inventive concepts presentedherein.

DETAILED DESCRIPTION

As described herein, an optical circuit includes solid state photonics.The optical circuit includes a phased array of solid state waveguidesthat perform beamsteering on an optical signal. The optical circuitincludes a modulator to modulate a bit sequence onto the carrierfrequency of the optical signal, and the beamsteered signal includes themodulated bit sequence. The optical circuit includes a photodetector todetect a reflection of the beamsteered optical signal. The opticalcircuit autocorrelates the reflection signal with the bit sequence togenerate a processed signal. The modulated signal can be lower powerthan a traditional signal because of the modulated bit sequence. Theautocorrelation can generate a processed signal that provides higherdepth resolution than traditional integrated optics circuits. Thus, theoptical circuit can use low power and still provide high resolutiondetection.

In one embodiment, the photonics circuit includes a LIDAR (lightdetection and ranging) circuit with a semiconductor-based steerablelaser. The optical frequencies of LIDAR enables gesture recognition andspatial mapping at high frame rates with millimeter precision due to thespatial resolution afforded by the small wavelength (on the order ofhundreds of nanometers) and diffraction limit of light. In oneembodiment, a LIDAR system outputs near-infrared light (having awavelength of approximately 700 nm), which is not visible to the humaneye and is compatible with commercially available components.Near-infrared signals are compatible with integrated semiconductoroptics based on phased array technology, which can steer a beam acrossthe field of view at high speed without the need for mechanically movingparts. Such an integrated optical system can include a photonic chipthat combines a laser and beamsteering circuitry.

LIDAR relies on collecting reflected light from diffuse surfaces, andthe signal degrades with the square of the distance. The degradation ofthe signal results in low signal to noise ratio (SNR) in the reflectedsignal. The low SNR typically demands a tradeoff between optical powerin a transmitted pulse, precision of the depth detection, and dwelltime. The optical power refers to the amount of current driven throughthe laser to create the optical signal, with increased current resultingin higher optical intensity/energy, which results in more reflections.Precision of the depth detection refers to the feature size of detectiondesired in the system, with lower precision possible with lower SNR.Dwell time refers to how long the LIDAR sweeps the target beforegenerating a detection signal. Longer dwell time can allow the opticalsystem to perform more precise detection.

Traditional approaches to LIDAR use high power optical signals toimprove the SNR and capture sufficient reflected power to detect objectsat a distance of several meters. VGA (video graphics array) resolutionand frame rates for such distant objects has traditionally requiredoptical power at levels in the hundreds of milliwatts that are notgenerally eye-safe, and levels that are incompatible with the powerconsumption requirements of portable and wearable devices. Portable andwearable devices can include smartphones as well as dedicated opticaldevices and camera equipment. VGA resolution and frame rates refers toresolutions that support approximately 640×480 pixel resolution, andtypically at 60 Hz refresh rates. Other resolutions and frame rates arepossible, but result in similar requirements for a dwell time per pixelof less than 60 ns.

In one embodiment, a LIDAR optical circuit includes a modulator tomodulate a bit sequence onto the carrier optical signal. The opticalsystem autocorrelates the reflection signals against the bit sequence togenerate a data signal. In one embodiment, the modulator can be referredto as a high speed modulator. It will be understood that high speed canbe a relative term, but for purposes herein, high speed can refer to asignal that enables the use of a pseudorandom bit sequence at least 64bits in length during the dwell time of the laser on a pixel of thefield of view. For example, for a dwell time of 60 ns per pixel (asrequires for VGA resolution at 60 Hz frame rate), use of a 64-bitpattern would require a 1 GHz signal, which can be considered highspeed. A signal length of 1024 bits could provide approximately 16 timesmore precise autocorrelation and therefore ranging precision, but wouldrequire a 16 GHz signal which can also be considered a high speedsignal. Thus, in one embodiment, a high speed modulator can refer to amodulator that modulates a high speed bit pattern signal onto thecarrier optical frequency.

Integrating a high speed modulator into a LIDAR circuit can improve thepower/precision/dwell tradeoff constraints when combined with solidstate beamsteering. Applying both solid state beamsteering and highspeed modulation enables an optical circuit to transmit a bit patterninstead of a single pulse, where the bit pattern is known to thereceiver. When the receiver knows the expected bit pattern, it canperform autocorrelation of the known signal with the returning “echo” orreflection signal, which can significantly improve the SNR and lower theoptical power needed for equivalent resolution detection.

In one embodiment, an optical circuit applies or modulates apseudorandom bit sequence (PRBS) or other coded pattern that allows forhigh processing gain. For example, a system can apply Golaycomplementary codes. Semiconductor optical circuits (such as siliconphotonics) are capable of generating GHz-speed modulation in opticalsignals. In one embodiment, a LIDAR system based on silicon photonics orother optical circuit that enables GHz-speed modulation applies patternsmeasuring hundreds or even thousands of bits in length to interrogateeach point in the far field without compromising frame rate orresolution.

In such a system, the SNR is improved by longer bit patterns withoutadding ambiguity in the timing/ranging since the pattern isnon-periodic. By integrating pseudorandom sequence generation withautocorrelation into solid state beamsteering optics, a system enablesnon-mechanical scanning from a small form-factor solution with SNR andperformance that is traditionally achievable only in much larger, lesspower efficient, and which require more processing and mechanicalcomplexity.

The traditional use of a modulator in an optical circuit allowsestablishment of a communication link by encoding the signal which is tobe transmitted onto the optical signal. The modulated signal carriesinformation to the other end of the communication link. The applicationof a modulator to an optical system as described herein modulates aknown signal onto the optical carrier. The known signal enables improvednoise rejection in a signal reflection or echo. The improved noiserejection enables higher depth perception or smaller feature detectionby being able to precisely detect time of flight information for thetarget object.

A LIDAR circuit as described herein can be one example of a LIDARcircuit in accordance with an embodiment of an optical circuit describedin U.S. patent application Ser. No. 14/318,604, entitled: “SOLID STATELIDAR CIRCUIT,” and filed Jun. 28, 2014. The following provides adescription of possible aspects of such an optical circuit.

In one embodiment, a solid state photonics circuit includes an array ofwaveguides disposed in either a semiconductor or an insulator, and ameans of phase tuning the optical signals in the waveguides in order tosteer the recombined beam. The phase steering mechanism can bethermooptic as described in [3], in which electrical heating elementsincorporated near the waveguides are used to change the optical phase ofthe signals, or electrooptic in which an applied voltage is used tochange the phase or absorption of the optical mode through thewell-known Franz Keldysh effect or the well-known Quantum Confined StarkEffect, or electrooptic in which a diode or capacitor incorporated intothe waveguide is used to alter either the concentration of electricalcharge interacting with the optical mode, thus altering the phasethrough the well-known effect of plasma dispersion, or using a liquidcrystal (LC) layer (which can specifically be liquid crystal on silicon(LCOS) when silicon photonics are used) selectively adjacent to thewaveguides. The waveguides have an adjacent insulating layer (e.g.,oxide), where the insulating layer has an opening to expose the array ofwaveguides to the LC layer. The LC layer can provide tuning for thearray of waveguides by controlling the application of voltage to theliquid crystal. The voltage applied to the LC layer can separately tuneall the waveguides. Applying different voltages to the LC layer cancreate phase shifts to steer the beam of laser light passing through thewaveguides. In one embodiment, the opening in the insulator exposes moreor less of different waveguides to produce a different phase shiftingeffect for each different waveguide.

It will be understood that LCOS beamsteering is only one example of apossible semiconductor steering mechanism that can be used in a solidstate LIDAR as referred to herein. In one embodiment, a LIDAR system inaccordance with what is described herein includes LC-based beamsteering.In one embodiment, a LIDAR system in accordance with what is describedherein includes a thermo-optic phase array. A thermo-optic phase arrayis an array of waveguides with resistive heaters placed in proximity ofthe waveguides. Control logic applies a current to the resistive heatersto create more or less heat. Based on the change in temperature, thephase of signals in the waveguides will vary. Control over the heatingcan control the phase of the signals and steer the beam.

In one embodiment, a LIDAR system in accordance with what is describedherein includes an electro-optic phase array. An electro-optic phasearray refers to an array of waveguides integrated with electrodes forapplication of either current or voltage to enable phase control viaelectro-optic deflection or modulation. Based on changing voltage orcurrent levels, the material's electro-optical properties cause a changein transmission of the optical signal through the waveguides based onchanges to one or more applied voltages or currents. Thus, control ofthe voltage or current can control phase of the signals in thewaveguides and steer the beam. A LIDAR system can thus provide asteerable laser via electro-optical modulation, thermo-optical phaseadjustment, liquid crystal beamsteering, or other beamsteering mechanismthat can be integrated with a waveguide array on a LIDAR integratedcircuit.

The use of solid state photonics allows the integration of photonicscomponents in a semiconductor substrate (e.g., silicon-based photonicsin a silicon substrate, and/or III-V based photonic elements integratedwith a silicon substrate). The photonics components can includewaveguides and combiners for routing light, passive elements that enablephased arrays for beam forming, one or more couplers to redirect lightperpendicular to the photonics substrate, and can include lasers,modulators, and/or detectors. In one embodiment, the semiconductorphotonics is silicon based, which allows the use of a standard siliconphotonic transmitter wafer. In one embodiment, the silicon photonicsprocessing incorporates III-V elements (e.g. Indium phosphide or GalliumArsenide) integrated with the silicon for purposes of lasing,amplification, modulation, or detection. In one embodiment, the standardsilicon photonics processing is extended to process liquid crystal ontothe silicon photonics. The LC enables a voltage-dependent change in therefractive index, which can enable both x and y beamsteering orbeamforming. Again, other forms of integrated phase control couldalternatively be used, such as thermo-optic phase control orelectro-optic phase control.

A basic LIDAR system includes one or more laser sources andphotodetectors, a means of scanning the beam(s) over the scene ofinterest or the target, and control logic to process the observed data.In one embodiment, the use of photonics processing extended with anintegrated phase control mechanism can enable the integration of a LIDARengine on a single chip, compatible with wafer-scale manufacturingtechnologies. The light sources and detectors (e.g., lasers andphotodetectors (PDs)) can be created on the same chip, or coupled to thesolid state LIDAR engine. In either case, the solid state LIDAR engineprovides a LIDAR engine with no moving parts, and which can bemanufactured at much lower cost than traditional LIDAR engines.Additionally, the use of semiconductor processing techniques allows thedevice to be low power and to have a much smaller form factor thantraditionally available. Additionally, the resulting LIDAR circuit doesnot need the traditional precision mechanical parts, which not onlyincrease costs, but suffer from vibration and other environmentaldisturbances. Furthermore, the solid state LIDAR would not requirehermetic sealing on the packaging, which is traditionally necessary toavoid dust and humidity from clogging the mechanics of the LIDAR system.

Reductions in power and size combined with improvements in reliability(reduced sensitivity to environmental factors) can increase theapplications of 3D imaging. 3D imaging with a solid state LIDAR canimprove functionality for gaming and image recognition. Additionally, 3Dimaging can be more robust for applications in replication of objectsfor 3D printing, indoor mapping for architecture or interior design,autonomous driving or other autonomous robotic movements, improvedbiometric imaging, and other applications. In one embodiment, the solidstate LIDAR described herein can be combined with inertial measurementcircuits or units to allow high resolution 3D imaging of a scene. Such acombined device would significantly improve on the low resolution ofconventional LIDAR system. The low resolution of traditional LIDARsystem is due to raster scanning a discrete series of point, whichdegrades spatial resolution.

A LIDAR circuit as described herein is not necessarily one example ofsuch a LIDAR circuit described in U.S. patent application Ser. No.14/318,604. To the extent that the following descriptions of thedrawings appear to conflict with descriptions of that patentapplication, the descriptions below can be understood to supersede theprevious patent application for purposes of the optical circuitsdescribed herein. To the extent such LIDAR technology is used, the LIDARcircuit can be extended in accordance with what is described herein, toenable the modulation of a known bit pattern and the autocorrelation ofa signal reflection with the known bit pattern to improve detection,even at lower transmission power.

FIG. 1 is a block diagram of an embodiment of a system with anintegrated solid state LIDAR circuit. System 100 represents any systemin which a solid state LIDAR that provides solid state beamsteering andapplies modulation can be used to provide 3D imaging. The solid stateLIDAR can be referred to as a LIDAR engine circuit or LIDAR circuit.Device 110 includes LIDAR 120 to perform imaging of target object 130.Target object 130 can be any object or scene (e.g., object against abackground, or group of objects) to be imaged. Device 110 generate a 3Dimage of object 130 by sending beamformed light 132 (a light signal) andprocessing reflections from the light signal.

Object 130 can represent an inanimate object, a person, a hand, a face,or other object. Object 130 includes feature 134, which represents afeature, contour, protrusion, depression, or other three dimensionalaspect of the object that can be identified with sufficient precision ofdepth perception. Reflected light 136 represents an echo or reflectionthat scatters off target object 130 and returns to LIDAR 120. Thereflection enables LIDAR 120 to perform detection.

Device 110 represents any computing device, handheld electronic device,stationary device, gaming system, print system, robotic system, cameraequipment, or other type of device that could use 3D imaging. Device 110can have LIDAR 120 integrated into device 110 (e.g., LIDAR 120 isintegrated onto a common semiconductor substrate as electronics ofdevice 110), or mounted or disposed on or in device 110. LIDAR 120 canbe a circuit and/or a standalone device. LIDAR 120 produces beamformedlight 132. In one embodiment, LIDAR 120 also processes data collectedfrom reflected light 136.

System 100 illustrates a close-up of one embodiment of LIDAR 120 in therotated inset. Traditional LIDAR implementations require mechanicalparts to steer generated light. LIDAR 120 can steer light without movingparts. It will be understood that the dimensions of elements illustratedin the inset are not necessarily to scale. LIDAR 120 includes substrate122, which is a silicon substrate or other substrate in or on whichphotonics or photonic circuit elements 140 are integrated. In oneembodiment, substrate 122 is a silicon-based substrate. In oneembodiment, substrate 122 is a III-V substrate. In one embodiment,substrate 122 is an insulator substrate. Photonics 140 include at leastan array of waveguides to convey light from a source (e.g., a laser, notspecifically shown) to a coupler that can output the light as beamformedlight 132.

The inset specifically illustrates liquid crystal beamsteeringcapability in LIDAR 120. It will be understood that alternativeembodiments of LIDAR 120 can include integrated thermo-optic phasecontrol components or electro-optic phase control components in photoniccircuit elements 140. While not specifically shown in system 100, itwill be understood that such applications represent an embodiment ofsystem 100. Referring more specifically to the illustration, insulator124 includes an opening (not seen in system 100) over an array ofwaveguides and/or other photonics 140 to selectively provide aninterface between photonics 140 and LC 126. In one embodiment, insulator124 is an oxide layer (any of a number of different oxide materials). Inone embodiment, insulator 124 can be a nitride layer. In one embodiment,insulator 124 can be another dielectric material. LC 126 can change arefractive index of waveguides in photonics 140. The opening ininsulator 124 can introduce differences in phase in the various lightpaths of the array of waveguides, which will cause multipledifferently-phased light signals to be generated from a single lightsource. In one embodiment, the opening in insulator 124 is shaped tointroduce a phase ramp across the various waveguides in the array ofwaveguides in photonics 140.

It will be understood that the shape in insulator 124 can change howmuch of each waveguide path is exposed to LC 126. Thus, application of asingle voltage level to LC 126 can result in different phase effects atall the waveguide paths. Such an approach is contrasted to traditionalmethods of having different logic elements for each different waveguidesto cause phase changes across the waveguide array. Differences in thesingle voltage applied to LC 126 (e.g., apply one voltage level for aperiod of time, and then apply a different voltage level) candynamically change and steer the light emitted from LIDAR 120. Thus,LIDAR 120 can steer the light emitted by changing the application of avoltage to the LCOS, which can in turn change the phase effects thatoccur on each waveguide path. Thus, LIDAR 120 can steer the light beamwithout the use of mechanical parts. Beamformed light 132 passes throughinsulator 124, LC 126, and a capping layer such as glass 128. The glasslayer is an example only, and may be replaceable by a plastic materialor other material that is optically transparent at the wavelength(s) ofinterest. The arrows representing beamformed light 132 in the inset aremeant to illustrate that the phases of the light can be changed toachieve a beam forming or steering effect on the light without having tomechanically direct the light.

In one embodiment, photonics 140 include an optical emitter circuit 142,which transfers light from waveguides within photonics towards targetobject 130 as beamformed light 132. In one embodiment, photonics 140include a modulator to modulate a known bit sequence or bit pattern ontothe optical signal that is emitted as beamformed light 132. In oneembodiment, photonics 140 include one or more photodetectors 144 toreceive reflected light 136. Photodetector 144 and photonics 140 conveyreceived light to one or more processing elements for autocorrelationwith the modulated bit sequence.

It will be understood that there are different types of LIDAR, includingtime-of-flight (TOF) and frequency modulated continuous wave (FMCW). Inone embodiment, LIDAR 120 is a TOF LIDAR system. In a TOF LIDAR systemthe beam can be modulated or pulsed such that the amplitude changes inthe received echo are compared and timed relative to the transmittedbeam, and the timing from send to receive is used to determinetime-of-flight and hence distance to the reflecting object.

FIG. 2 is a block diagram of an embodiment of a system with anintegrated solid state LIDAR circuit that autocorrelates a reflectionsignal with a known bit sequence. System 200 provides one example of aLIDAR system in accordance with an embodiment of system 100. System 200is illustrated in a format that might approximate an embodiment of anoptical chip based on silicon photonics. It will be understood thatcomponents are not necessarily shown to scale, or shown in a practicallayout. The illustration of system 200 is to provide one example of aLIDAR as described herein, without necessarily illustrating layoutdetails.

Photonics IC (integrated circuit) represents a chip and/or circuit boardon which photonics components are disposed. At a silicon-processinglevel, each component disposed on photonics IC 210 can be integrated viaoptical processing techniques to create active components (such asdrivers, lasers, processors, amplifiers, and other components) andpassive components (such as waveguides, mirrors, gratings, couplers, andother components). Other components are possible. At another level,photonics IC 210 may be a system on a chip (SoC) substrate, with one ormore components integrated directly onto the substrate, and one or morecomponents disposed as separate ICs onto the SoC. At a circuit boardlevel, photonics IC 210 could actually be a PCB (printed circuit board)onto which discrete components (such as a laser and a coupler) aredisposed in addition to a core LIDAR engine IC enabled to generate asteerable light source.

In one embodiment, photonics IC 210 includes light source 222, such as alaser. In one embodiment, light source 222 includes an off-chip laser.In one embodiment, light source 222 includes an integrated on-chiplaser. An on-chip laser can be made, for example, from III-Vsemiconductor material bonded to a silicon-on-insulator chip substrate,with waveguides integrated in the silicon layer and gain provided by theIII-V materials. Light source 222 passes an optical signal throughmodulator 224, which modulates a signal onto the optical carrier.Modulator 224 can be a high speed modulator. In one embodiment,modulator 224 can be a Mach-Zehnder modulator using either carrierdepletion, carrier injection, or an applied electrical field to applyphase tuning to the two arms of an interferometer, thus creatingconstructive and destructive interference between the optical beamspropagating in the two arms to induce amplitude modulation. In anotherembodiment, modulator 224 can be an electro-absorption modulator usingcarrier injection, carrier depletion, or an applied electrical field tocause absorption of the optical beam and thus induce amplitudemodulation. In one embodiment, modulator 224 can be embodied in asilicon layer of system 200. In one embodiment where system 200 includesIII-V material, modulator 224 can be integrated into the III-V materialor both in silicon and III-V. The modulated signal will enable system200 to autocorrelate reflection signals to perform depth detection of anobject and/or environment. In one embodiment, signal source 226represents an off-chip source of the bit pattern signal to be modulatedonto the optical signal. In one embodiment, signal source 226 can beintegrated onto photonics IC 210.

In one embodiment, modulator 224 passes the modulated optical signal tooptical control 232. Optical control 232 represents elements withinphotonics IC 210 to can amplify, couple, select, and/or otherwise directoptical power via a waveguide to the phased array for phase control.Phased array 234 represents components on photonics IC 210 to applyvariable phase control to separated optical signals to enablebeamsteering by photonics IC 210. Thus, photonics IC 210 combinesoptical signal modulation with a LIDAR engine that generates steerablelight. Emitter 240 represents an emitter mechanism, such as a gratingcoupler or other coupler that emits light off-chip from the on-chipwaveguides.

Beam 242 represents a light beam generated by photonics IC 210.Beamsteering 244 represents how photonics IC 210 can steer beam 242 inx-y coordinates with respect to a plane of the surface of photonics IC210 on which the components are disposed. While not necessarily to scaleor representative of a practical signal, beam 242 is illustrated asbeing overlaid with modulation 246 to represent the modulation generatedby modulator 224. Phase array 234 can include optical components and/orfeatures to phase-offset a modulated optical signal split among variouswaveguides, with each phase-delayed version of the optical signal to betransmitted in turn, based on the delay. The delays introduced canoperate to steer beam 242. In one embodiment, modulation 246 is a 20Gb/s signal generated by modulator 224 to impress a long-code bitpattern sequence onto beam 242. In one embodiment, modulator 224generates a 2 Gb/s signal. It will be understood that generally a highermodulation speed will further improve SNR (for example, see the exampleof FIG. 8).

To be a complete LIDAR system, system 200 includes one or more detectorsto capture reflections of beam 242. In one embodiment, PD 250 representsa detector integrated with the LIDAR engine circuit. It will beunderstood that PD 250 can be on a separate chip from the beamsteeringoptics. Similarly, while photonics IC 210 is illustrated havingintegrated light source 222, a laser could be on a chip separate fromthe beamsteering optics. In one embodiment, PD 250 receives light from areverse path of waveguides used to transmit beam 242. In one embodiment,PD 250 has a separate received light path.

PD 250 can be or include a high bandwidth photodiode and one or moreamplifier circuits. PD 250 passes received light to autocorrelator 260.In one embodiment, autocorrelator 260 is off-chip from photonics IC 210.In one embodiment, autocorrelator 260 is part of a processor orcontroller that performs signal processing to determine depthinformation based on the received reflection and on the known bitsequence modulated onto the optical signal. In one embodiment, signalsource 226 generates a pseudorandom bit sequence (PRBS) for modulator224 to modulate onto a laser beam. A PRBS can be a sequence of pulsewith white space between. In one embodiment, signal source 226 passesthe bit sequence to modulator 224 and to autocorrelator 260. In oneembodiment, signal source 226 generates a signal and stores it onphotonics IC 210, such as in pre-deployment configuration and/or testingoperations.

In one embodiment, a laser (e.g., light source 222), amplifier,modulator (e.g., 224), and/or detector (e.g., PD 250), or anycombination thereof may be integrated on silicon using III-V material(e.g. Indium Phosphide based semiconductor incorporating variouscompatible quaternary or ternary compounds to act as quantum wells,contact layers, confinement layers, or carrier blocking layers). SuchIII-V components can be attached to the silicon or to an intermediatelayer. In an embodiment using III-V material, the III-V material canprovide gain, modulation, and/or absorption for optical modes whichpropagate through the silicon. Thus, III-V material can be used tointegrate a laser, an amplifier, a modulator, and/or a photodetectoron-chip.

In one embodiment, the bit pattern encoded by modulator 224 includes along bit pattern. While “long” can be relative, in general the long bitpattern refers to a bit pattern in the hundreds or thousands of bits.The longer a bit pattern can be, the more it can improve SNR, althoughthe length of the bit pattern needs to be weighed against the requireddwell time (how long to hold a beam at a location in a sweep orsteering) for the length of the bit pattern. By encoding a long bitpattern onto the signal, the timing of the return signal can bedetermined with higher precision by comparing the known transmittedpattern with the returned echo. In one embodiment, a bit pattern of 1112bits in length showed a 26 dB improvement in SNR over a beam without themodulation, other conditions being the same. For implementationsinvolving a limited dwell time of the beam on a particular point in thefar field, such as when used in a rapidly scanning gesture recognitionsystem, depth precision and low power operation can be enhanced by usinga high bit rate for modulation in modulator 224. The higher bit rateenables a longer bit pattern to be encoded and transmitted withoutsacrificing scanning speed. Testing at bit rates of multiple Gb/s havedemonstrated significant SNR improvements, and silicon photonics withintegrated modulation are compatible with these bit rates as well aseven higher bit rates in the tens of Gb/s for superior SNR withoutincreasing dwell time on a particular pixel.

In one embodiment, the LIDAR system of system 200 is not a coherentdetection system. With coherent detection, the system relies oncoherently interfering the received echo with a reference signal. System200 enables autocorrelation by comparing a reflected pulse or bitpattern with the transmitted pulse or bit pattern, where the two neednot be interfered coherently. The system thus only needs information onthe power of the reflected system, rather than its phase. The decodingincludes comparing bit patterns rather than comparing phase of thesignals. The timing information can be derived from the offset in theautocorrelation, which then indicates depth. It will be understood thatshorter, repeated patterns could be applied by modulator 224. However,such repeated patterns introduce periodicity, making it difficult todetermine what the offset is between the transmitted and receivedsignals without ambiguity.

FIG. 3A is a block diagram of an embodiment of a photonic system thatautocorrelates a reflection signal with a known bit sequence, with asingle transmitter and receiver I/C. System 302 illustrates one exampleof a photonic system in accordance with an embodiment of system 100and/or an embodiment of system 200. Photonic IC 320 integratesoptical/photonic components that enable modulating a bit sequence onto asteerable beam to transmit to a target. Photonic IC 320 further includesone or more detection components to receive signal reflections, and sendthe reflections for autocorrelation to determine depth information fromthe transmitted signal. In one embodiment, photonic IC 320 is a siliconphotonics chip.

DC source 312 represents a power source for system 302. In particular,DC source 312 provides power to enable laser 322 to generate an opticalsignal or laser beam. In one embodiment, laser 322 includes acontinuous-wave laser. In one embodiment, the modulation can be externalmodulation of a signal onto the laser which can enable the signal to bemodulated independently of phase-steering. Alternatively, the laser canbe pulsed to generate a bit pattern, in which case an external modulatormay not be required. In one embodiment, the bit sequence modulation isperformed via amplitude modulation. Thus, in one embodiment, modulator324 represents an amplitude modulator or other modulator that inserts adata bit sequence onto the laser signal. Modulator 324 can be a highspeed modulator, indicating that the bit sequence has a data rate atleast 64 times higher than rate at which the optical signal is switchedfrom one pixel to the next as it is scattered off the target. In oneembodiment, code generator 314 generates a PRBS for modulation onto thecarrier frequency of the optical signal. In one embodiment, codegenerator 314 represents an off-chip pseudorandom sequence generator. Inone embodiment, code generator 314 generates a long code sequence,referring to a bit sequence being hundreds of bits or more. In oneembodiment, code generator 314 is part of a processor that interfaceswith photonic IC 320.

Coupler 326 represents an optical component to convey the modulatedoptical signal an amplifier component. SOA (semiconductor opticalamplifier) 328 represents an optical component that amplifies theoptical signal. SOA 328 amplifies the optical signal to split the signalinto multiple waveguides. Mux/demux 330 represents a waveguidedemultiplexer for transmitted signals and a waveguide multiplexer forreceived signals. Mux/demux 330 could alternatively be referred to as asplitter/combiner. The optical signal is split into multiple differentwaveguides in phased array 332. In one embodiment, beam control 350generates a phase offset among the multiple waveguides of phased array332. Thus, beam control 350 can change the relative phase of the signalsand electrically steer the output beam, instead of using mechanicalmeans to steer the beam. In one embodiment, photonics IC 320 includesmonitor photodetector 336 to tap off optical power to feed back intobeam control 350, to enable beam control 350 to appropriately adjust thebeamsteering operation of phased array 332.

Phased array 332 conveys the signals to one or more emitter portions ofemitter array 334 for transmission from photonic IC 320. Phased array332 is steerable based on control signals from beam control 350. Phasedarray 332 and output emitter array 334 are integrated on a single chipwith modulator 324 to generate and steer a beam encoded with a bitsequence towards a target. Emitter array 334 outputs steered beam 342via lens 340 toward the target. In one embodiment, lens 340 is anadjustable lens, which can be focused differently to allow for wider ornarrower transmission and reception. Wider transmission spreads thetransmitted signal further. Wider reception enables focusing morereflected signals. Narrower transmission enables more focusedtransmission and can reduce scattering. Narrower reception reduces theamount of reflection light that might be received.

In one embodiment, reflection signal 344 returns via lens 340 throughthe coupler of emitter array 334, and is conveyed back through thewaveguides of phased array 332, via mux 330 to SOA 328, and to coupler326. In one embodiment, coupler 326 can couple a transmitted signal frommodulator 324 to SOA 328, and can couple a received signal from SOA 328to photodetector 338. In one embodiment, photodetector 338 is ahigh-bandwidth photodiode that receives the reflected signal fordetection. In one embodiment photodetector 338 is integrated on-chip onphotonics IC 320 with phased array 332, as illustrated. Thus,photodetector 338 can be integrated on a common substrate of photonicsIC 320.

In one embodiment, photodetector 338 conveys the received signal to TIA(transimpedance amplifier) 360 to convert and amplify the optical signalinto a digital signal. Autocorrelator 370 represents autocorrelationlogic or circuitry for system 302. In one embodiment, autocorrelator 370is part of a processor or signal processor associated with photonic IC320. In one embodiment, autocorrelator 370 includes digitalautocorrelation logic or circuitry, to apply digital signal processingtechniques to compare the bit pattern of the received signal to the bitpattern generated by code generator 314. In one embodiment,autocorrelator 370 includes analog autocorrelation logic or circuitry tocombine the received signal with the generated bit pattern to determinehow long the signal took to return. With either digital or analogautocorrelation, system 302 can determine how long reflection 344 tookto return, which can indicate how far away the target is.

It will be understood that the bit pattern modulated onto steered beam342 enables system 302 to detect a much weaker signal reflection 344than is possible without the bit pattern and autocorrelation processing.Thus, system 302 can enable the use of a lower power laser pulse, whilestill offering high precision range detection.

FIG. 3B is a block diagram of an embodiment of a photonic system thatautocorrelates a reflection signal with a known bit sequence, withseparate transmitter and receiver I/Cs. System 304 illustrates oneexample of a photonic system in accordance with an embodiment of system100 and/or an embodiment of system 200. System 304 is an alternative tosystem 302 of FIG. 3A. System 302 illustrates photonic IC 320 with anintegrated photodetector 338 for receiving reflection signals. System304 includes a photodetector off-chip from photonic IC 380. Asingle-chip design such as illustrated by system 302 provides noisereduction as light comes in through only a single lens to a singlephotonics IC. A two-chip design such as illustrated by system 304provides more light to the detector, but with more ambient light.

When the receiver is on the same chip as the transmitter as in system302, the reflection returns through the same collection lens and phasedarray used to steer the beam. When the receiver is on a separate chip asin system 304, the receiver chip will have a separate optical path forreceived light than the optical path for transmitted light of thetransmitter chip. In either case, in one embodiment, the photonics ICcan include a modulator to encode a bit pattern onto the beam forautocorrelation and improved SNR. In one embodiment, in either systemthe autocorrelation can be accomplished using a reference signaldirectly from the code generator that generates the bit sequence formodulation. In one embodiment, in either system the autocorrelation canbe accomplished using the modulated output from the optical modulatorand an additional high-bandwidth PD for so-called “true photonicmonitoring.”

Where components of system 304 are numbered the same as components ofsystem 302, the description of the components can be considered to bethe same or similar to what is described above. Photonic IC 380integrates optical/photonic components that enable modulating a bitsequence onto a steerable beam to transmit to a target. Photonic IC 380is separate from detection components to receive signal reflections, asillustrated by separate lens 380 and high bandwidth photodetector 384.The separate detector sends the reflections for autocorrelation todetermine depth information from the transmitted signal. In oneembodiment, photonic IC 380 is a silicon photonics chip.

DC source 312, laser 322, modulator 324, code generator 314, coupler326, POA 328, mux 330, phased array 332, emitter array 334, monitor PD336, and beam control 350 of photonic IC 380 can be the same as similarcomponents in photonic IC 320 of system 302. As with system 302 system304 includes lens 340, and emitter array 334 generates steered beam 342for transmission to a target. Instead of receiving reflections via lens340 for an on-chip photodetector, system 304 includes separate lens 390to receive reflections 382. In one embodiment, high bandwidthphotodetector 384 receives reflections 382 and sends them to TIA 386.TIA 386 can amplify the received optical signals and pass them toautocorrelator 370.

In one embodiment, autocorrelator 370 performs the autocorrelation withthe modulated optical signal generated on photonic IC 380. In oneembodiment, coupler 326 couples the modulated optical signal frommodulator 324 to photodetector 338. In one embodiment, photodetector 338passes the signal to TIA 360, which provides an amplified signal toautocorrelator 370.

FIG. 4 is a block diagram of an embodiment of a top view of anintegrated solid state LIDAR circuit. System 400 represents elementsincluding a solid state LIDAR circuit, which can be one example of aLIDAR in accordance with an embodiment of system 100, system 200, system302, or system 304. In one embodiment, system 400 includes laser 410,which could be separate from the LIDAR circuit. Laser 410 is a lightsource for system 400. In one embodiment, laser 410 can be integrated onthe same circuit as the LIDAR. Laser 410 could be integrated directly onthe same substrate that includes the photonic components. Such animplementation can provide a self-contained steerable laser. Laser 410could also be combined in a multichip package or system on a chiparrangement where laser 410 is a separate die combined in package and/oron the same substrate as the photonics. Laser 410 could also be includedas a separate chip (off chip) from the LIDAR photonics.

In one embodiment, system 400 includes modulator 420. In one embodiment,modulator 420 can provide amplitude modulation to the laser signal. Theamplitude modulation can be added, for example, to a pulsed laser. Theamplitude modulation can include a bit sequence from sequence source 422that provides a modulated bit signal. The modulated signal can enableautocorrelation with a known bit sequence for improved SNR in thereflected signal. In one embodiment, system 400 modulates the lasersignal to impress a bit pattern upon it before directing it to the farfield (to the target) and a detector times the echo. Other rangingimplementations are possible.

In one embodiment, system 400 includes amplifier 416, which can includeor be a semiconductor optical amplifier, for example a semiconductoroptical amplifier composed of III-V material attached to a siliconsubstrate. In one embodiment, amplifier 416 can couple the modulatedsignal to high bandwidth photodetector (PD) 470. In one embodiment, PD470 provides the signal to amplifier 472, which in turn provides thesignal to autocorrelator 474. In one embodiment, reflection signalsreturn via the same optical path as signals for transmission from system400, which can be routed back to PD 470. Autocorrelator 474 performsautocorrelation on such a reflection compared to the bit sequencegenerated by sequence source 422, which could separately pass the bitsequence to the autocorrelator. In one embodiment, the path fromamplifier 416 to PD 470 to amplifier 472 to autocorrelator 474represents a path to pass the modulated transmit signal forautocorrelator 474 to use in autocorrelation with a separate reflectionsignal (e.g., via a detector not shown in system 400).

In one embodiment, system 400 includes splitter 430, which can be ademultiplexer or other mechanism that splits the source light from laser410 into N channels, such as 8, 16, 24, or some other number ofchannels. The N channels are illustrated by waveguides 0 through [N−1](WG[0] through WG[N−1]). The N channels or waveguides represent a phasedarray. N can be any number of channels that will provide properresolution for the LIDAR. It will be understood that there are manydifferent ways to split an optical signal. Splitter 430 can thereforevary from one implementation to another. In one embodiment, splitter 430is or includes a multimode interference (MMI) coupler. In oneembodiment, splitter 430 is or includes a star coupler.

From splitter 430, the light signal is carried through the array ofwaveguides or phased array along path 432, which is a path from splitter430 to coupler 450. Coupler 450 allows system 400 to emit the light fromthe various channels. In one embodiment, path 432 includes right anglebends to route the waveguides to coupler 450. Bends in the waveguidescan allow the introduction of spacing between the waveguides of thearray, and are not necessarily right angle bends. The spacing can allowthe introduction of phase offsets between the waveguides relative toeach other. The phase offsets or phase shifting provides phasedifferences in the laser signal that enables beam forming and beamsteering in the emitted wavefront. In one embodiment, it can be possibleto introduce spacing differences in splitter 430, or in some other wayin system 400; thus, the right angle bends in the array of waveguidesmay not be needed in one embodiment.

In one embodiment, path 432 passes the array of waveguides through tuner440. Tuner 440 represents a mechanism in system 400 that introducesrelative phase offsets in the various waveguides of the array. In oneembodiment, tuner 440 includes an opening in an oxide layer (or otherinsulator layer or insulating layer, where oxide is used as anon-limiting example) that is adjacent the photonics components of theLIDAR. The opening in the oxide exposes the waveguide channels to theliquid crystal of an LCOS layer (or other LC layer, where LCOS is usedas a non-limiting example) adjacent the oxide layer. In one embodiment,the opening can be triangular to expose the channels to more and more ofthe liquid crystal to create a linear phase shift across the channels.For example, assuming the triangular shape of tuner 440 to be the shapeof the opening in the oxide, WG[0] is exposed to less of the liquidcrystal than WG[1], because WG[0] is closer to the apex of the trianglethan WG[1]. There is also less of WG[1] exposed to less of the liquidcrystal than there would be for WG[2] (not explicitly shown), and soforth from one adjacent waveguide to another until WG[N−1], which is themost exposed to the liquid crystal. WG[N−1] is shown as being locatednearest the base of the illustrated triangle. There would be a linearphase shift from WG[0] to WG[N−1] based on the voltage applied to theliquid crystal. Thus, the liquid crystal can act as a single tuner forall channels which steers the emitted beam from side to side.

It will be understood that instead of using an opening in the oxide anda voltage applied to a liquid crystal layer, system 400 could includecontrol logic to introduce a delay signal to each waveguideindividually. Such a tuning mechanism might require more power and wouldrequire significantly more logic than the LCOS tuning mechanism.Alternatively, system 400 can include thermo-optical components inproximity with the waveguides to control signal phase. Different sizecomponents and/or different current applications to different componentscan provide phase control over the signals in the waveguides.Alternatively, system 400 can include electro-optical components withinthe waveguide array to control signal phase. The application ofdifferent voltages or currents at different points of the array canprovide phase control. In an embodiment with either thermo-opticcomponents (not specifically shown) or electro-optic components (notspecifically shown), tuner 440 can take on a different physicalimplementation in accordance with an appropriate integrated structurethat enables the application of heat-based phase tuning, voltage-basedphase tuning, or current-based phase tuning.

In an embodiment where LCOS is applied, it will be understood that theopening in the oxide layer does not have to match what is shown, but canbe a right triangle, or could be a trapezoid or other shape. There couldalso be a configuration where the phase shifts are not linear from oneside of the waveguide array to another, but different shapes of openingcould be used to introduce other delay into the waveguide. For example,an opening could be formed to expose a waveguide in the middle of thearray to the least amount of liquid crystal, and be of a complex shapethat in some other way introduces different delays to the differentwaveguides. While the principles discussed would be the same for suchconfigurations, the illustration of system 400 offers a simpler solutionthan such complex oxide opening patterning.

Control logic 442 represents logic in system 400 that can control thebeam forming of light from the waveguides of the array. In oneembodiment, system 400 includes control logic that interacts with anLCOS layer or other phase control circuitry to introduce phase shiftingthe in the waveguides. In one embodiment, system 400 includes controllogic to interact with the waveguides to introduce the phase shifting.In one embodiment, system 400 includes control logic to interact withcoupler 450 to control the emission of light from system 400. In oneembodiment, system 400 includes control logic to align the signals inthe various waveguides prior to introducing the desired phase offsets.For example, splitter 430 and/or path 432 could introduce differentdelays into the waveguide signals, relative to one another. Such delayswould normally be considered within the operating tolerances of aphotonics circuit. However, to carefully control the phase delay forpurpose of controlling the beam forming of the signals, system 400 cancompensate and/or account for other delays or phase shifts introducedinto the waveguides. Thus, tuning can start with all channels havinguniform phase, to more precisely introduce the desired phase delays.Alternatively, the shaping or operation of tuner 440 can compensate forexpected phase delays introduced by the architecture of the photonics insystem 400.

In one embodiment, system 400 can provide both X and Y beam steering,relative to the axes shown in system 400. A phased array as described,where phase shifting is introduced into different waveguides of thearray, can provide x-axis beam steering. In one embodiment, system 400includes one or more mechanisms to introduce a variable refractive indexon the output of light from coupler 450, which can introduce y-axis beamsteering.

The light or laser signal is output from system 400 by coupler 450. Thedirection of propagation of the signal from coupler 450 would typicallybe in a z-axis relative to the axes shown in system 400. The lightsignal is sent to the target to cause far field interference. Light willbe reflected back toward system 400 as scattered light after interferingwith the far field. It will be understood that a complete LIDAR systemwill include one or more detectors (e.g., photodetectors) to receive thereflected light that interfered in the far field. The receptors ordetectors then send signals to a processor or control logic to interpretthe signals. In one embodiment, system 400 includes detectors on chipwith the other LIDAR photonics components. Such detectors are notexplicitly shown. The detectors could alternatively be off-chip. Thedetectors provide the reflection signals to autocorrelator 474 forautocorrelation compared to the transmitted bit sequence of thetransmitted light. The autocorrelation can improve the SNR for depthperception of system 400.

FIGS. 5A-5B are block diagrams of an embodiment of cross sections of anintegrated solid state LIDAR circuit. Circuit 500 represents elements ofa solid state LIDAR engine chip, and can be an example of a solid stateLIDAR in accordance with an embodiment described herein. In oneembodiment, circuit 500 is based on silicon photonics circuits asillustrated, but in another embodiment, other semiconductorarchitectures can be used to create a solid state LIDAR chip. FIG. 5Aillustrates an embodiment of a cross section of the LIDAR enginephotonics. FIG. 5B illustrates the LIDAR engine photonics of FIG. 5Afrom a cross section view of a portion of a silicon waveguide array.

Circuit 500 includes SOI (silicon on insulator) substrate 510, which canbe used as a substrate on which to process silicon photonics. Oxidelayer 520 can represent the insulator of substrate 510. Siliconwaveguide 532 can be processed into substrate 510 to couple light fromlaser 550 to coupler 534. In one embodiment, laser 550 is integrateddirectly on substrate 510 (and can include a modulator). In oneembodiment, what is illustrated as laser 550 represents an area wherelaser light is coupled into circuit 500 from an off-chip laser. Siliconwaveguide 532 represents the waveguide array, as mentioned herein, andas shown more specifically in FIG. 5B.

Oxide 540 represents an oxide layer or cladding oxide adjacent thephotonics components, and covers the silicon photonics of circuit 500.Oxide 540 includes opening 542, which exposes waveguide 532 to liquidcrystal 560. Thus, circuit 500 more specifically illustrates an exampleof an LCOS phase control circuit. It will be understood that otherimplementations of phase tuning are also possible, as described herein.In the cross section of FIG. 5B, oxide 540 is not shown, because thecross section is provided for an area of circuit 500 where waveguides532 are not covered by oxide 540, but are exposed to liquid crystal 560(i.e., opening 542). In one embodiment, liquid crystal 560 is an areasurrounded by seal 562 that is processed on substrate 510. In oneembodiment, such processing is part of a different processing routinethan what is used to create the silicon or other semiconductor photonicscomponents. The different processing routine is not necessarily evencarried out on the same processing line or processing facility. Glass570 is a cap layer for circuit 500, and represents a material that isoptically transparent at the wavelength(s) of interest, referring to thewavelength(s) of light emitted via coupler 534.

Coupler 534 represents a coupling mechanism that changes the directionof the light signal, to emit the signal that travels through waveguide532 to pass out through glass 570 to the imaging target. In oneembodiment, coupler 534 is a grating coupler. In one embodiment, coupler534 is a mirror-based coupler. In one embodiment, coupler 534 representsan array of couplers, just as waveguide 532 represents a waveguidearray. There can be a coupler for each waveguide, or anotherconfiguration that will allow the phase delayed signals to emit out ofcircuit 500. It will be understood that gratings are wavelengthdependent. But by wavelength tuning the laser, system 500 can steer thebeam even with a wavelength dependent grating.

It will be understood that liquid crystal 560 needs two electrodes tocreate a voltage that causes the phase shifting in waveguide array 532.In one embodiment, electrode 582 is located between liquid crystal layer560 and glass layer 570. In one embodiment, electrode 584 is locatedbetween waveguide 532 and oxide 520. Applying a voltage betweenelectrodes 582 and 584 can change an index of refraction of interfacebetween liquid crystal 560 and waveguide 532. In one embodiment,electrode 582 is an indium tin oxide (ITO) material. In one embodiment,electrode 584 is a material deposited on oxide 520. In anotherembodiment, system 500 biases liquid crystal 560 directly to thewaveguide, in which case electrode 584 can represent doping of waveguide532. By adjusting the electric field on liquid crystal 560 next towaveguide 532, system 500 can change the phase delay, which willsteer/form the wave front of the emitted beam. The electric field nearwaveguide 532 can be changed by applying a voltage between siliconfeatures within the wafer (electrode 584) and/or a voltage on theelectrode on the glass wafer (electrode 582). The phase change can occurvia thermal phase control or based on a free carrier effect.

Similar to what is described with respect to system 400, circuit 500 cangenerate 3D data from a scene without the use of mechanical beamsteeringor broadcast illumination. Liquid crystal 560 interfaces directly withwaveguides 532 via opening 542 in oxide 540. Liquid crystal 560 createsa phased array of signals from the light signals split into an array ofwaveguides 532. Overlaid liquid crystal 560 can tune the refractiveindex of each beam component as provided in the separate waveguides 532by application of a voltage. The waveguides transfer the phased array ofsignals to coupler(s) 534, which can also be referred to as emitters, totransmit the signals out of system 500. Thus, the light signal can be asteered beam emitted from the circuit or chip and monitoring hardware(e.g., photodetectors and processing hardware) can monitor a far fieldbeam shape formed by the relative phases introduced into the individualcomponents of the optical signal.

Circuit 500 can provide several advantages over traditional LIDARsystems. In one embodiment, circuit 500 can provide a single-chipsolution, fully integrated with lasers and detectors and batchfabricated using existing fabrication processes. Such a single-chipsolution can provide substantial cost savings in space as well as thecost of manufacture. The primary cost of traditional LIDAR systemsarises from the complex and precise assembly of many optical andmechanical elements, which can be eliminated with an embodiment ofsystem 500. In one embodiment, a LIDAR system in accordance with system500 does not include any moving parts, but can perform all beam steeringelectrically via application of voltages to electrodes 582 and 584 (andthus to liquid crystal 560). System 500 is also inherently lower poweras compared to traditional LIDAR system, given that the steeringmechanism does not involve any motorization, but rather voltage appliedacross a solid-state capacitor to vary the field in the liquid crystal.As discussed above, varying the field in the liquid crystal canphase-adjust the components of the beam as transferred in each separatewaveguide 532. In one embodiment, system 500 can reduce sensitivity ofthe LIDAR to ambient light or other nearby LIDAR systems by encoding thebeam with an on-chip modulator (not specifically shown in 500, but canbe included in accordance with an embodiment described herein).

In one embodiment, while not explicitly shown, system 500 includes anintegrated high speed modulator to modulate a high bit rate signal ontothe optical beam for transmission. Modulating a known bit sequence ontothe transmitted optical beam enables a receiver associated with system500 to receive reflected light and send it to processing logic toperform autocorrelation. The autocorrelation can be in accordance withany embodiment described herein, where a detected signal reflection iscompared with the known bit sequence to perform the autocorrelation.

FIG. 6 is a diagrammatic representation of a pseudorandom bit sequencemodulated onto a phased LIDAR output signal for an embodiment of aphotonic integrated circuit. Diagrams 602 and 604 illustrate an exampleof signal-to-noise improvement by autocorrelating a known PRBStransmitted signal with a noisy return signal. Diagram 602 shows noisysignal 612, which has PRBS pattern 614 encoded into it beginning at 10ns, at signal start 622. Combined signal 616 represents the combinationof noisy signal 612 with PRBS pattern 614 encoded into it.

Diagram 604 includes the same time axis 632, and is aligned with diagram602 along axis 632. Diagram 604 illustrates one example of anautocorrelation function of PRBS pattern 614 with noisy signal612/combined signal 616. Although the signal is too noisy to see theencoded bit pattern from the autocorrelation in diagram 604, theautocorrelation shows a clear peak 624 at 10 ns corresponding to signalstart 622, or the location of the bit stream in the noise. In oneembodiment, peak 624 identifies when the reflection signal comes back.Whether the autocorrelation represented in diagram 604 is performeddigitally as a buffered and processed signal with a delay circuit, orwhether performed as an analog overlay (with a linear phase shift andmultiplication) of the transmit pattern and the receive signal, in oneembodiment, the autocorrelation can identify a peak or other indicationof the detection of the signal. Peak 624 can be used by signalprocessing circuits to determine timing related to the signal, anddetermine ranging and depth information from the timing.

FIG. 7 is a diagrammatic representation of a plot of signal to noise forpseudorandom bit sequences of different bandwidth for an embodiment of asolid state LIDAR circuit. Diagram 702 illustrates one example of a plotof calculated range resolution versus required SNR for a 50 nscollection time. Diagram 702 was generated from theoretical calculationsof a LIDAR system using high speed modulation and digitalautocorrelation. The results are generally representative of expectedbehavior of a photonic IC with modulation and autocorrelation inaccordance with any embodiment described herein.

Diagram 702 illustrates simulated results of achievable depth precisionversus required SNR for two separate bit rate, as calculated accordingto the Cramer-Rao lower bound. Diagram 702 illustrates the effects ofbit pattern modulation data rate on SNR. SNR 712 (measured in dB) isplotted against the log of resolution 714 (measured in millimeters). Bymodulating a known bit pattern onto an optical signal of a LIDAR systemand autocorrelating that modulated bit pattern with signal echoesdetected by a receiver, the system can adjust the tradeoff.

Signal 722 represents a 2 GHz signal or 2 Gb/s signal modulated into aranging light beam. It will be observed at point 732 on the graph thatfor 1 mm depth precision, which is the precision needed to capturefacial expression changes and/or hand/finger gestures, 2 GHz signal 722requires nearly 20 dB SNR. Signal 724 represents a 20 GHz signal or a 20Gb/s signal modulated into the ranging light beam. It will be observedat point 734 on the graph that for the same 1 mm depth precision, 20 GHzsignal 724 requires only 6 dB SNR. Such performance is achievable inaccordance with an embodiment of a LIDAR system described herein.

It will be understood that the autocorrelation as described does notrequire coherent detection. Rather, standard square-law detectionprovides sufficient performance because the bit pattern is used todetermine the delay of the returning reflection signal, rather than thephase of the optical carrier. The delay of the returning reflectionsignal can be used to calculate range to the reflector in the far-field,where the reflector is a surface of a target object or environment beingscanned.

FIG. 8 is a flow diagram of an embodiment of a process for imaging witha solid state LIDAR circuit. An embodiment of process 800 for 3D imagingcan be executed by a solid state LIDAR engine in accordance with anembodiment described herein. A LIDAR system generates a source laserlight signal, 802. In one embodiment, the laser is a laser integrated onthe same LIDAR engine circuit that includes a phased waveguide array andbeamsteering circuitry. In one embodiment, the LIDAR system includes amodulator to modulate a bit pattern into the source light, 804. In oneembodiment, the modulation is amplitude modulation. The modulation canbe high-speed modulation of a PRBS signal. In one embodiment, themodulated optical signal can be used as a reference signal forautocorrelation of the bit pattern in a received reflection.

In one embodiment, the LIDAR system amplifies the optical signal andpropagates the modulated source laser light to multiple waveguides of aphased array, 806. The propagation to the phased array can include theuse of couples, multiplexer/demultiplexer, splitter, and/or othercomponents. The phased array can include any type of phase control thatcan be integrated into a LIDAR circuit, such as those described herein.In one embodiment, the LIDAR system applies a phase change to theoptical signals in the waveguides, 808. The application of the phasechange can beamsteer the optical signal. Other beamsteering operationscan also or alternatively be performed. In one embodiment, the systemmonitors the optical signal to determine how to adjust the beam forsweeping across a target, 810.

If the system determines to change the beamforming, 812 YES branch, inone embodiment, the system applies a new phase change to the opticalsignal, 808. If no beamforming changes are needed, 812 NO branch, in oneembodiment, the system propagates the phase adjusted optical signal toan emitter or emitter array to transmit to the target object, 814. Thetransmitted signal will reflect off the target and cause reflections toreturn to the LIDAR system. The LIDAR system can receive thereflections, including capturing reflected light with one or morephotodetectors, 816. In one embodiment, the LIDAR system amplifies andpropagates the reflection signal to the photodetectors, 818. Thedetectors can be on the same chip as the LIDAR engine, or a differentchip.

In one embodiment, the LIDAR system passes the received light to anautocorrelation circuit to autocorrelate the reflection signal with thePRBS signal pattern, 820. The autocorrelation can provide much higherprecision to ranging determinations, resulting in a high precision LIDARthat does not require a high power output signal. The autocorrelationlogic can pass the autocorrelation information to a processor thatcomputes ranging information based on the autocorrelation information,822. The processing can include signal processing to generate a 3D imageor mapping of the target.

FIG. 9 is a block diagram of an embodiment of a computing system inwhich a low power, high resolution solid state LIDAR circuit can beimplemented. System 900 represents a computing device in accordance withany embodiment described herein, and can be a laptop computer, a desktopcomputer, a server, a gaming or entertainment control system, a scanner,copier, printer, routing or switching device, or other electronicdevice. System 900 includes processor 920, which provides processing,operation management, and execution of instructions for system 900.Processor 920 can include any type of microprocessor, central processingunit (CPU), processing core, or other processing hardware to provideprocessing for system 900. Processor 920 controls the overall operationof system 900, and can be or include, one or more programmablegeneral-purpose or special-purpose microprocessors, digital signalprocessors (DSPs), programmable controllers, application specificintegrated circuits (ASICs), programmable logic devices (PLDs), or thelike, or a combination of such devices.

Memory subsystem 930 represents the main memory of system 900, andprovides temporary storage for code to be executed by processor 920, ordata values to be used in executing a routine. Memory subsystem 930 caninclude one or more memory devices such as read-only memory (ROM), flashmemory, one or more varieties of random access memory (RAM), or othermemory devices, or a combination of such devices. Memory subsystem 930stores and hosts, among other things, operating system (OS) 936 toprovide a software platform for execution of instructions in system 900.Additionally, other instructions 938 are stored and executed from memorysubsystem 930 to provide the logic and the processing of system 900. OS936 and instructions 938 are executed by processor 920. Memory subsystem930 includes memory device 932 where it stores data, instructions,programs, or other items. In one embodiment, memory subsystem includesmemory controller 934, which is a memory controller to generate andissue commands to memory device 932. It will be understood that memorycontroller 934 could be a physical part of processor 920.

Processor 920 and memory subsystem 930 are coupled to bus/bus system910. Bus 910 is an abstraction that represents any one or more separatephysical buses, communication lines/interfaces, and/or point-to-pointconnections, connected by appropriate bridges, adapters, and/orcontrollers. Therefore, bus 910 can include, for example, one or more ofa system bus, a Peripheral Component Interconnect (PCI) bus, aHyperTransport or industry standard architecture (ISA) bus, a smallcomputer system interface (SCSI) bus, a universal serial bus (USB), oran Institute of Electrical and Electronics Engineers (IEEE) standard1394 bus (commonly referred to as “Firewire”). The buses of bus 910 canalso correspond to interfaces in network interface 950.

System 900 also includes one or more input/output (I/O) interface(s)940, network interface 950, one or more internal mass storage device(s)960, and peripheral interface 970 coupled to bus 910. I/O interface 940can include one or more interface components through which a userinteracts with system 900 (e.g., video, audio, and/or alphanumericinterfacing). Network interface 950 provides system 900 the ability tocommunicate with remote devices (e.g., servers, other computing devices)over one or more networks. Network interface 950 can include an Ethernetadapter, wireless interconnection components, USB (universal serialbus), or other wired or wireless standards-based or proprietaryinterfaces.

Storage 960 can be or include any conventional medium for storing largeamounts of data in a nonvolatile manner, such as one or more magnetic,solid state, or optical based disks, or a combination. Storage 960 holdscode or instructions and data 962 in a persistent state (i.e., the valueis retained despite interruption of power to system 900). Storage 960can be generically considered to be a “memory,” although memory 930 isthe executing or operating memory to provide instructions to processor920. Whereas storage 960 is nonvolatile, memory 930 can include volatilememory (i.e., the value or state of the data is indeterminate if poweris interrupted to system 900).

Peripheral interface 970 can include any hardware interface notspecifically mentioned above. Peripherals refer generally to devicesthat connect dependently to system 900. A dependent connection is onewhere system 900 provides the software and/or hardware platform on whichoperation executes, and with which a user interacts.

In one embodiment, system 900 includes solid state LIDAR 980, which canbe or include a photonics IC in accordance with any embodiment describedherein. In one embodiment, LIDAR 980 is a system that includes one ormore chips, which allows the LIDAR to perform non-mechanical beamforming/steering of a light signal to perform 3D imaging. LIDAR 980includes a modulator to modulate a bit sequence onto the optical rangingsignal, such as a PRBS bit pattern, and includes or provides detectedlight to an autocorrelator to perform autocorrelation of the modulatedbit sequence with the received signal. The autocorrelation can providemore precise timing detection, improving the SNR for signal reflections,and improving the resolution of range detection. In one embodiment,LIDAR 980 can be a single chip that is packaged together with othercomponents of system 900. In one embodiment, LIDAR 980 sends imaginginformation (which can include reference signals) to processor 920 forprocessing. LIDAR 980 can include a LIDAR engine circuit in accordancewith any embodiment described herein, and enables system 900 for avariety of different imaging applications with a high resolution, lowpower optical system.

FIG. 10 is a block diagram of an embodiment of a mobile device in whicha low power, high resolution solid state LIDAR circuit can beimplemented. Device 1000 represents a mobile computing device, such as acomputing tablet, a mobile phone or smartphone, a wireless-enablede-reader, wearable computing device, or other mobile device. It will beunderstood that certain of the components are shown generally, and notall components of such a device are shown in device 1000.

Device 1000 includes processor 1010, which performs the primaryprocessing operations of device 1000. Processor 1010 can include one ormore physical devices, such as microprocessors, application processors,microcontrollers, programmable logic devices, or other processing means.The processing operations performed by processor 1010 include theexecution of an operating platform or operating system on whichapplications and/or device functions are executed. The processingoperations include operations related to I/O (input/output) with a humanuser or with other devices, operations related to power management,and/or operations related to connecting device 1000 to another device.The processing operations can also include operations related to audioI/O and/or display I/O.

In one embodiment, device 1000 includes audio subsystem 1020, whichrepresents hardware (e.g., audio hardware and audio circuits) andsoftware (e.g., drivers, codecs) components associated with providingaudio functions to the computing device. Audio functions can includespeaker and/or headphone output, as well as microphone input. Devicesfor such functions can be integrated into device 1000, or connected todevice 1000. In one embodiment, a user interacts with device 1000 byproviding audio commands that are received and processed by processor1010.

Display subsystem 1030 represents hardware (e.g., display devices) andsoftware (e.g., drivers) components that provide a visual and/or tactiledisplay for a user to interact with the computing device. Displaysubsystem 1030 includes display interface 1032, which includes theparticular screen or hardware device used to provide a display to auser. In one embodiment, display interface 1032 includes logic separatefrom processor 1010 to perform at least some processing related to thedisplay. In one embodiment, display subsystem 1030 includes atouchscreen device that provides both output and input to a user.

I/O controller 1040 represents hardware devices and software componentsrelated to interaction with a user. I/O controller 1040 can operate tomanage hardware that is part of audio subsystem 1020 and/or displaysubsystem 1030. Additionally, I/O controller 1040 illustrates aconnection point for additional devices that connect to device 1000through which a user might interact with the system. For example,devices that can be attached to device 1000 might include microphonedevices, speaker or stereo systems, video systems or other displaydevice, keyboard or keypad devices, or other I/O devices for use withspecific applications such as card readers or other devices.

As mentioned above, I/O controller 1040 can interact with audiosubsystem 1020 and/or display subsystem 1030. For example, input througha microphone or other audio device can provide input or commands for oneor more applications or functions of device 1000. Additionally, audiooutput can be provided instead of or in addition to display output. Inanother example, if display subsystem includes a touchscreen, thedisplay device also acts as an input device, which can be at leastpartially managed by I/O controller 1040. There can also be additionalbuttons or switches on device 1000 to provide I/O functions managed byI/O controller 1040.

In one embodiment, I/O controller 1040 manages devices such asaccelerometers, cameras, light sensors or other environmental sensors,gyroscopes, global positioning system (GPS), or other hardware that canbe included in device 1000. The input can be part of direct userinteraction, as well as providing environmental input to the system toinfluence its operations (such as filtering for noise, adjustingdisplays for brightness detection, applying a flash for a camera, orother features). In one embodiment, device 1000 includes powermanagement 1050 that manages battery power usage, charging of thebattery, and features related to power saving operation.

Memory subsystem 1060 includes memory device(s) 1062 for storinginformation in device 1000. Memory subsystem 1060 can includenonvolatile (state does not change if power to the memory device isinterrupted) and/or volatile (state is indeterminate if power to thememory device is interrupted) memory devices. Memory 1060 can storeapplication data, user data, music, photos, documents, or other data, aswell as system data (whether long-term or temporary) related to theexecution of the applications and functions of system 1000. In oneembodiment, memory subsystem 1060 includes memory controller 1064 (whichcould also be considered part of the control of system 1000, and couldpotentially be considered part of processor 1010). Memory controller1064 includes a scheduler to generate and issue commands to memorydevice 1062.

Connectivity 1070 includes hardware devices (e.g., wireless and/or wiredconnectors and communication hardware) and software components (e.g.,drivers, protocol stacks) to enable device 1000 to communicate withexternal devices. The external device could be separate devices, such asother computing devices, wireless access points or base stations, aswell as peripherals such as headsets, printers, or other devices.

Connectivity 1070 can include multiple different types of connectivity.To generalize, device 1000 is illustrated with cellular connectivity1072 and wireless connectivity 1074. Cellular connectivity 1072 refersgenerally to cellular network connectivity provided by wirelesscarriers, such as provided via GSM (global system for mobilecommunications) or variations or derivatives, CDMA (code divisionmultiple access) or variations or derivatives, TDM (time divisionmultiplexing) or variations or derivatives, LTE (long termevolution—also referred to as “4G”), or other cellular servicestandards. Wireless connectivity 1074 refers to wireless connectivitythat is not cellular, and can include personal area networks (such asBluetooth), local area networks (such as WiFi), and/or wide areanetworks (such as WiMax), or other wireless communication. Wirelesscommunication refers to transfer of data through the use of modulatedelectromagnetic radiation through a non-solid medium. Wiredcommunication occurs through a solid communication medium.

Peripheral connections 1080 include hardware interfaces and connectors,as well as software components (e.g., drivers, protocol stacks) to makeperipheral connections. It will be understood that device 1000 couldboth be a peripheral device (“to” 1082) to other computing devices, aswell as have peripheral devices (“from” 1084) connected to it. Device1000 commonly has a “docking” connector to connect to other computingdevices for purposes such as managing (e.g., downloading and/oruploading, changing, synchronizing) content on device 1000.Additionally, a docking connector can allow device 1000 to connect tocertain peripherals that allow device 1000 to control content output,for example, to audiovisual or other systems.

In addition to a proprietary docking connector or other proprietaryconnection hardware, device 1000 can make peripheral connections 1080via common or standards-based connectors. Common types can include aUniversal Serial Bus (USB) connector (which can include any of a numberof different hardware interfaces), DisplayPort including MiniDisplayPort(MDP), High Definition Multimedia Interface (HDMI), Firewire, or othertype.

In one embodiment, system 1000 includes solid state LIDAR 1090, whichcan be or include a photonics IC in accordance with any embodimentdescribed herein. In one embodiment, LIDAR 1090 is a system thatincludes one or more chips, which allows the LIDAR to performnon-mechanical beam forming/steering of a light signal to perform 3Dimaging. LIDAR 1090 includes a modulator to modulate a bit sequence ontothe optical ranging signal, such as a PRBS bit pattern, and includes orprovides detected light to an autocorrelator to perform autocorrelationof the modulated bit sequence with the received signal. Theautocorrelation can provide more precise timing detection, improving theSNR for signal reflections, and improving the resolution of rangedetection. In one embodiment, LIDAR 1090 can be a single chip that ispackaged together with other components of system 1000. In oneembodiment, LIDAR 1090 sends imaging information (which can includereference signals) to processor 1010 for processing. LIDAR 1090 caninclude a LIDAR engine circuit in accordance with any embodimentdescribed herein, and enables system 1000 for a variety of differentimaging applications with a high resolution, low power optical system.

In one aspect, an optical circuit includes: a phased array of solidstate waveguides to receive an optical signal and transmit the opticalsignal as a beamsteered optical signal; a modulator circuit coupled tomodulate a bit sequence onto a carrier frequency of the optical signal;and a photodetector to detect a reflection signal of the beamsteeredoptical signal, and transmit the reflection signal for autocorrelationwith the bit sequence to generate a processed signal.

In one embodiment, the bit sequence comprises a pseudorandom bitsequence (PRBS). In one embodiment, the PRBS comprises a series of PRBSpulses separated by white noise. In one embodiment, the photodetectorcomprises a photodetector circuit integrated on a common substrate withthe phased array, wherein the photodetector and the phased array share acommon optical lens. In one embodiment, the photodetector comprises aphotodetector circuit integrated on a substrate separate from asubstrate of the phased array. In one embodiment, the autocorrelationcomprises digital autocorrelation. In one embodiment, theautocorrelation comprises analog autocorrelation. In one embodiment, theautocorrelation comprises non-coherent autocorrelation on the reflectionsignal.

In one aspect, an electronic device includes: an integrated photoniccircuit including a phased array of solid state waveguides to receive anoptical signal and transmit the optical signal as a beamsteered opticalsignal; a modulator circuit coupled to modulate a bit sequence onto acarrier frequency of the optical signal; and a photodetector to detect areflection signal of the beamsteered optical signal; a processor toautocorrelate the reflection signal with the bit sequence to generate aprocessed signal; and an adjustable lens coupled to focus thetransmitted optical signal from the phased array.

In one embodiment, the bit sequence comprises a pseudorandom bitsequence (PRBS). In one embodiment, the PRBS comprises a series of PRBSpulses separated by white noise. In one embodiment, the photodetectorcomprises a photodetector circuit integrated on a common substrate withthe phased array. In one embodiment, the photodetector comprises aphotodetector circuit integrated on a substrate separate from asubstrate of the phased array. In one embodiment, the processor toautocorrelate the reflection signal comprises a processor with digitalautocorrelation logic. In one embodiment, the processor to autocorrelatethe reflection signal comprises a processor with analog autocorrelationlogic. In one embodiment, the processor to perform non-coherentautocorrelation on the reflection signal.

In one aspect, a method for range detection includes: modulating a bitsequence onto a carrier frequency of an optical signal; receiving theoptical signal with the modulated bit sequence at a phased array ofsolid state waveguides; transmitting the optical signal with themodulated bit sequence from the phased array of solid state waveguidesas a beamsteered optical signal; receiving a reflection signal from thetransmitted signal reflecting off an object; and autocorrelating thereflection signal with the bit sequence to generate a processed signal.

In one embodiment, modulating the bit sequence comprises a modulating apseudorandom bit sequence (PRBS). In one embodiment, the PRBS comprisesa series of PRBS pulses combined with noise. In one embodiment, the PRBScomprises a series of PRBS pulses separated by white noise. In oneembodiment, the photodetector comprises a photodetector circuitintegrated on a common substrate with the phased array, wherein thephotodetector and the phased array share a common optical lens. In oneembodiment, receiving the reflection signal comprises receiving thereflection signal with a photodetector circuit integrated on a commonsubstrate with the phased array. In one embodiment, autocorrelatingcomprises performing digital autocorrelation. In one embodiment,autocorrelating comprises performing analog autocorrelation. In oneembodiment, autocorrelating comprises performing non-coherentautocorrelation on the reflection signal.

Flow diagrams as illustrated herein provide examples of sequences ofvarious process actions. The flow diagrams can indicate operations to beexecuted by a software or firmware routine, as well as physicaloperations. In one embodiment, a flow diagram can illustrate the stateof a finite state machine (FSM), which can be implemented in hardwareand/or software. Although shown in a particular sequence or order,unless otherwise specified, the order of the actions can be modified.Thus, the illustrated embodiments should be understood only as anexample, and the process can be performed in a different order, and someactions can be performed in parallel. Additionally, one or more actionscan be omitted in various embodiments; thus, not all actions arerequired in every embodiment. Other process flows are possible.

To the extent various operations or functions are described herein, theycan be described or defined as software code, instructions,configuration, and/or data. The content can be directly executable(“object” or “executable” form), source code, or difference code(“delta” or “patch” code). The software content of the embodimentsdescribed herein can be provided via an article of manufacture with thecontent stored thereon, or via a method of operating a communicationinterface to send data via the communication interface. A machinereadable storage medium can cause a machine to perform the functions oroperations described, and includes any mechanism that stores informationin a form accessible by a machine (e.g., computing device, electronicsystem, etc.), such as recordable/non-recordable media (e.g., read onlymemory (ROM), random access memory (RAM), magnetic disk storage media,optical storage media, flash memory devices, etc.). A communicationinterface includes any mechanism that interfaces to any of a hardwired,wireless, optical, etc., medium to communicate to another device, suchas a memory bus interface, a processor bus interface, an Internetconnection, a disk controller, etc. The communication interface can beconfigured by providing configuration parameters and/or sending signalsto prepare the communication interface to provide a data signaldescribing the software content. The communication interface can beaccessed via one or more commands or signals sent to the communicationinterface.

Various components described herein can be a means for performing theoperations or functions described. Each component described hereinincludes software, hardware, or a combination of these. The componentscan be implemented as software modules, hardware modules,special-purpose hardware (e.g., application specific hardware,application specific integrated circuits (ASICs), digital signalprocessors (DSPs), etc.), embedded controllers, hardwired circuitry,etc.

Besides what is described herein, various modifications can be made tothe disclosed embodiments and implementations of the invention withoutdeparting from their scope. Therefore, the illustrations and examplesherein should be construed in an illustrative, and not a restrictivesense. The scope of the invention should be measured solely by referenceto the claims that follow.

What is claimed is:
 1. An optical circuit comprising: a modulator toreceive an optical signal and modulate a bit sequence onto a carrierfrequency of the optical signal; a group of solid state waveguidescoupled to the modulator to convey the optical signal for emission froma group of optical emitters, the emission including beamsteering themodulated signal with the bit sequence; and a photodetector to detect anecho, the echo being a reflection signal of the emitted signal, andtransmit the echo for autocorrelation with the bit sequence to determinea time of flight of the emitted signal.
 2. The optical circuit of claim1, wherein the bit sequence comprises a non-periodic pattern of bits. 3.The optical circuit of claim 2, wherein the bit sequence comprises apseudorandom bit sequence (PRBS).
 4. The optical circuit of claim 3,wherein the PRBS comprises a series of PRBS pulses separated by whitenoise.
 5. The optical circuit of claim 1, wherein the bit sequencecomprises hundreds of bits.
 6. The optical circuit of claim 1, whereinthe photodetector comprises a photodetector circuit integrated on acommon substrate with the group of solid state waveguides, wherein thephotodetector and the group of solid state waveguides share a commonoptical lens.
 7. The optical circuit of claim 1, wherein thephotodetector comprises a photodetector circuit integrated on asubstrate separate from a substrate of the group of solid statewaveguides.
 8. The optical circuit of claim 1, wherein theautocorrelation comprises digital autocorrelation.
 9. The opticalcircuit of claim 1, wherein the autocorrelation comprises analogautocorrelation.
 10. The optical circuit of claim 1, wherein theautocorrelation comprises non-coherent autocorrelation on the reflectionsignal.
 11. A sensor device comprising: an integrated photonic circuitincluding a modulator to receive an optical signal and modulate a bitsequence onto a carrier frequency of the optical signal; and a group ofsolid state waveguides coupled to the modulator to convey the opticalsignal for emission from a group of optical emitters, the emissionincluding beamsteering the modulated signal with the bit sequence; and aphotodetector to detect an echo, the echo being a reflection signal ofthe emitted signal, and transmit the echo for autocorrelation with thebit sequence to determine a time of flight of the emitted signal; and anadjustable lens coupled to focus the emitted optical signal from thegroup of solid state waveguides.
 12. The sensor device of claim 11,wherein the bit sequence comprises a non-periodic pattern of bits. 13.The sensor device of claim 12, wherein the bit sequence comprises apseudorandom bit sequence (PRBS).
 14. The sensor device of claim 13,wherein the PRBS comprises a series of PRBS pulses separated by whitenoise.
 15. The sensor device of claim 11, wherein the bit sequencecomprises hundreds of bits.
 16. The sensor device of claim 11, whereinthe photodetector comprises a photodetector circuit integrated on acommon substrate with the group of solid state waveguides, wherein thephotodetector and the group of solid state waveguides share a commonoptical lens.
 17. The sensor device of claim 11, wherein thephotodetector comprises a photodetector circuit integrated on asubstrate separate from a substrate of the group of solid statewaveguides.
 18. The sensor device of claim 11, wherein theautocorrelation comprises digital autocorrelation.
 19. The sensor deviceof claim 11, wherein the autocorrelation comprises analogautocorrelation.
 20. The sensor device of claim 11, wherein theautocorrelation comprises non-coherent autocorrelation on the reflectionsignal.